Abstract

Most commercially available sports drinks contain 6%-8% carbohydrate (CHO). The present study systematically evaluated the effects of lower concentrations of CHO on physical and mental performance. Twelve healthy males (mean±SD age 22±2 years; height 181±8 cm; mass 73.5±8.1 kg; VO2max 4.0±0.5 l/min) exercised to volitional exhaustion at a workload corresponding to 70% VO2max at 10°C, 60% RH. Subjects ingested 3 ml/kg body mass of a 0%, 2%, 4% or 6% CHO solution immediately before exercise and a further 1.5 ml/kg body mass of the appropriate solution every 10 min during exercise. Heart rate, core temperature, perceived exertion and thermal stress were recorded at regular intervals. Expired gas samples were collected to determine rates of substrate utilisation. Cognitive function was assessed using a computerised test battery. Exercise time to exhaustion was 102.6±33.9 min, 109.2±33.9 min, 121.0±25.7 min and 122.4±29.9 min in the 0%, 2%, 4% and 6% trials, respectively (p=0.012). Drink CHO content did not influence heart rate (p=0.261) or core temperature (p=0.545). Rates of CHO (p=0.244) and fat (p=0.136) oxidation were not influenced by the treatment, but total CHO utilisation was greater during the 4% (454±125 g) and 6% (441±118 g) trials than on the 0% (325±105 g) and 2% (364±106 g; p=0.001). Exercise resulted in a slowing of response times to a visual search task in all trials (p=0.006). This response appeared to be attenuated by CHO ingestion during the complex/interference level, but this just failed to reach significance (p>0.05). The present study demonstrated a progressive increase in endurance performance with increasing CHO concentration. There was some suggestion that CHO may also attenuate decrements in motor skills tasks performed after exhausting exercise. The study was carried out in relation to the product Powerade and was funded in part by The Coca-Cola Company.

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